Kristin Cavallari's secret to slim post-baby body less than six months after giving birth? Healthy eating and no alcohol! Us Weekly caught up with the new mom, 26, at the launch of her jewelry capsule collection for Glamboutique in L.A. on Tuesday, Feb. 5. While there, she shared her son Camden's latest milestones and revealed how she got in such great shape.

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"I'm like a freak about eating healthy," she told Us. "I've always been a really healthy eater. I think when I got pregnant I took it up another notch, just because I was so aware of what I was putting in my body. I've just maintained that since I've had Cam. And honestly, I rarely drink alcohol, which helps too. It's just empty calories."

Since the former Hills star welcomed her first child with fiance Jay Cutler in August 2012, however, she hasn't completely deprived herself of sweets.

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"I have a huge sweet tooth but I'll get dark chocolate with caramel," she explained. "Or there's an ice cream at Whole Foods called Coconut Bliss, which is made out of coconut milk, and so, to me, that's not really cheating." 

And occasionally, she'll even eat fast food -- but only twice a year! "There's a place called Portillo's in Chicago which is fast food [and] has the best burgers," Cavallari, who splits her time between L.A. and Chicago to be with her 29-year-old Chicago Bears quarterback beau, shared. "So we've had that I think twice this year. But that's a lot of fast food for me in that short amount of time," she added with a laugh.

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The first-time mom also has her son eating healthy too. "He's almost six months," she gushed. "He's getting his two bottom teeth and he just started eating food, which has been a ton of fun."

"I'm getting organic food and then steaming it for a few minutes and then blending it up," Cavallari explained. "Right now he loves avocados and he also loves zucchini."

This article originally appeared on Kristin Cavallari on Her Slim Post-Baby Body: "I'm a Freak About Eating Healthy"